Conductive pressure sensitive textile

ABSTRACT

A fabric including within its construction a first elongated electrical conductor crossed by a second elongated electrical conductor, the conductors being normally biased apart at a crossover point of said fibres with an air gap between them, whereby application of pressure in a direction substantially normal to a plane of the fabric causes the conductors to make contact. The fabric may be woven, knitted, non-woven or plaited. The fabric can be used as a pressure sensor, switch or other sensor.

FIELD OF THE INVENTION

The present invention relates to methods of constructing one or morepressure activated electrical switches or sensors in fabric, in thepreferred embodiment as integral elements of a single fabric sheet.

BACKGROUND OF THE INVENTION

Electrically conductive fabric sheets are known in the art and aredescribed, for example in the applicant's earlier British patentapplication 2,339,495. The known conductive fabric sheets typicallycomprise two conductive layers separated by an insulating layer whichcan be bridged upon application of pressure on the conductive layers.Although such fabric assemblies can function well, there are inevitabledrawbacks with having to have three or more fabric layers, includingadditional cost, fabric thickness, need to maintain alignment betweenthe various layers, movement of the layers during use and so on.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved conductive textile.According to an aspect of the present invention, there is provided afabric as specified in claim 1.

The preferred embodiment provides a woven, knitted, non-woven or plaitedfabric including in its woven, knitted, non-woven or plaitedconstruction a first elongated electrical conductor crossed by a secondelongated electrical conductor, the conductors being normally biasedapart at the crossover point with an air gap between them whereby theapplication of pressure normal to the plane of the fabric causes theconductors to make contact.

Preferably, the fabric includes a plurality of spaced first conductorsand/or a plurality of spaced second conductors thereby forming aplurality of said crossover points. The conductors may compriseelectrically conductive filaments or fibres.

Advantageously, the fabric is a woven fabric; the warp of which mayinclude at least one said first electrical conductor and the weft mayinclude at least one said second electrical conductor.

A number of means may be employed, separately or in combination, to biasthe conductors apart at the crossover points; in one preferredembodiment this being achieved by including insulating fibres orfilaments in the fabric. For example, the biasing apart may be effectedby employing, as at least one of the electrical conductors, anelectrical conductor having insulating filament or fibre wound round itto leave the surface of the conductor exposed at the crossover point. Inanother example, the biasing apart is effected by twisting at least oneof the electrical conductors together with insulating filament or fibre.Alternatively, the biasing apart may be effected by employing, as atleast one of the electrical conductors, an electrical conductor which issupported on and between deformable protuberances of an insulatingfilament or fibre. In another embodiment, the biasing apart may beeffected by including in the weave warp and/or weft floats over morethan one yarn.

It is preferred that the electrical conductors have an electricalproperty which is proportional to or reproducible from the length of theconductor. The length of a conductor or plurality of connectingconductors may then be determined from measurement of that property.Advantageously, the electrical property is resistance.

For some applications, it will be advantageous for the fabric to have atleast one set of spaced electrical conductors, at least some of said setbeing electrically connected together to form at least one bus bar.Where said set of spaced electrical conductors comprise electricallyconductive filaments or fibres in the warp or weft of a wovenconstruction, electrical connection between conductors of that set maybe provided by one or more electrically conducting filaments or fibresin the weft or warp, respectively. Alternatively, said electricalconnection may be effected after the weaving process.

In a preferred embodiment, there is provided a fabric including aplurality of weft fibres and a plurality or warp fibres, first andsecond conductive fibres within the weft and warp fibres and at leastone insulating fibre within the weft and/or warp fibres, the insulatingfibre acting to bias apart said first and second conductive fibres so asto provide space therebetween.

The fabric may include a plurality of insulating fibres within one ofthe weft and warp fibres, which insulating fibres provide a bridge for aconductive fibre in the other of the weft and warp fibres, such thatsaid conductive fibre floats over one or more conductive fibres in theone of the weft and warp fibres.

In another embodiment, one or more insulating fibres is provided aroundat least one of the conductive fibres, for example helically disposedtherearound. Alternatively, one or more conductive fibres could beprovided around at least one insulating fibre, with the insulating fibreincluding portions, for example projections, extending beyond theperimeter of the conductive fibre or fibres. The insulating fibre canthus provide the spacing means for spacing the conductor from otherconductors within the fabric layer.

It will be apparent that the invention can provide a conductive textilefor a pressure sensor or switch or other conductive device within asingle layer of fabric. This can obviate the problems discussed above.

In addition, it is possible to reduce the edge effect (non-linearity ofresistance relative to position) which is intrinsic to three-layerstructures and which must be corrected for to provide accuratemeasurements. Moreover, it is possible to have significantly higherresolution, possibly ten times or more, relative to the three layerdevice; the resolution being dependent upon weaving techniques and fibredimensions.

With the preferred embodiments, it is possible to provide for contact ofthe conductive fibres upon the application of a specific pressure orpressures to the fabric and this can be determined by the size of theair gap, the tension of the weave, the deformability of the conductorsand the compressibility of the insulators. Moreover, it is possible toprovide a range of pressure sensitivities within a single fabricstructure. For example, with the embodiment of floating conductor(described with reference to FIG. 3 below) different pressuresensitivities can be provided with a plurality of bridges having adifferent number of conductors below the bridges and/or differentinsulating fibres, such as different thicknesses or compressibilities.Similar effects can be envisaged with respect to the other embodimentsof fibre disclosed herein.

As an alternative, there can be provided two or more layers of thedescribed fabric, having the same or different structures.

According to another aspect of the present invention, there is provideda fibre including a conductive yarn around which is wrapped at least oneinsulating yarn. Preferably, there are provided two or more insulatingyarns helically wound around the conductive yarn.

According to another aspect of the present invention, there is provideda fibre including an insulating yarn around which is wrapped at leastone conductive yarn, the insulating yarn including portions extendingbeyond the conductive yarn or yarns. Preferably, there are provided twoor more conductive yarns helically wound around the insulating yarn. Theprojecting portions could be strands of fibre, protrusions and the like.

It is possible with the present invention to provide an electricallyconductive textile having the features described in British patentapplication 2,339,495 with only a single layer of fabric.

The preferred embodiments of fabric can be significantly cheaper toproduce than the structure described in British patent application2,339,495.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are described below, by wayof example only, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a grid arrangement of elongateconductors;

FIG. 2 depicts the effects of applied pressure on a crossover betweentwo conductors;

FIG. 3 is a perspective view of an embodiment of fabric with floatingconductors;

FIG. 4 shows the operation of the fabric of FIG. 3;

FIG. 5 shows various views of an embodiment of yarn;

FIG. 6 shows various views of another embodiment of yarn;

FIGS. 7 a to 7 c show various embodiments of conductive and insulatingyarns;

FIG. 8 shows another embodiment of composite yarn;

FIG. 9 shows variations of the embodiment of yarn with floatingconductors;

FIG. 10 is a schematic diagram of an embodiment of woven bus bars;

FIG. 11 shows an example of technical specification of weave structure;and

FIG. 12 shows an example of individually addressable multiplexedswitches within a woven fabric construction.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to the Figures, in the embodiment of FIG. 1, the piece offabric preferably comprises at least two sets of elongate electricalconductors. Typically, the conductors in each set are arranged inparallel relative to one another and one set of conductors is arrangedperpendicular relative to the other set to form an arbitrarily spacedgrid, as shown in FIG. 1. The elongated electrical conductors aretypically mono-filament or multi-filament conductive fibres, while theremainder of the piece of fabric is composed of insulating fibres.

Where any two conductors cross over one another, the construction of thefabric and/or the conductive fibres maintains their physical separation,as shown in the cross-sectional view of two conductors in FIG. 2( a).When pressure is applied normal to the plane of the fabric, theconductive fibres are caused to deflect and make electrical contact, asin FIG. 2( b). Thus, each crossover point constitutes a momentarycontact electrical switch, which will maintain contact while the appliedpressure exceeds a threshold. The threshold pressure can bepredetermined and controlled at manufacture.

The switches also exhibit an analogue switching region, as the area ofcontact shared by the two conductors varies according to the appliedpressure, until a maximum contact area is achieved, as shown in FIG. 2(c). The manufacturing variables of the piece of fabric can be controlledsuch that, in use, the switches operate predominantly within thisanalogue region, demarcated by the dashed lines in FIG. 2( d). If thisarea of contact is measured through some electrical property, forinstance resistance, the crossovers can constitute pressure sensors.

Although the piece of fabric can be of knitted or felted construction,it is envisaged that the primary application of this technology will beto woven fabric structures. In this latter case, the two sets ofconductive fibres can constitute warp and weft yarns, respectively, withinsulating yarns composing the remainder of the piece of fabric andacting to space apart the individual conductive yarns of each set. Atypical example of a woven piece of fabric, incorporating two crossoverpoints, is shown in FIG. 3.

Separation Techniques

A number of techniques can be used for maintaining a degree of physicalseparation between two conductive fibres at a crossover point. Thesetechniques include the use of weave structures with floated yarns andcomposite conductive/insulating yarns. The different techniques may beused together, allowing, for example, a piece of fabric thatincorporates both conductive cored composite yarn and a weave structurewith floats.

Separation Technique—Weaving with Floats over One or More Yarns

The first described separation technique is the use of a weave structurewith floats, a term applied to a portion of weft yarn that passes overor under more than one warp yarn or vice-versa. To achieve separation ofthe two conductive yarns at a crossover, typically, the weft conductiveyarn is floated over the warp conductive yarn and one or more insulatingwarp yarns to either side, as is shown in FIG. 3. As a result, the twoconductive yarns share little or no physical contact area, as shown inthe cross-sectional view, longitudinal to the weft, of FIG. 4( a).

If the conductive warp yarn is of smaller diameter than the surroundinginsulating warp yarns, their physical separation can be effected, asshown in FIG. 4( b). When pressure is applied normal to the plane of thefabric, the yarns and surrounding fabric deflect, and the two conductorsmake electrical contact, as in FIG. 4( c). Increasing applied pressureincreases the area of contact, as in FIG. 2( c). The yarns must exhibitsufficient elasticity to recover from the deflection upon removal of theapplied pressure, and thus return to their separated positions, breakingthe electrical contact.

Separation Technique—Conductive Cored Yarn Encircled with DisplaceableInsulator

Another separation technique involves using a specific compositeconstruction for the conductive yarns. In this composite yarn, aconductive mono-filament or multi-filament core yarn is twisted,braided, spun, plaited, co-moulded, coated, sleeved or otherwisepartially encircled by insulating material, as shown in FIG. 5( a).

When a crossover point between two conductive yarns, at least one ofwhich is of this nature, is not subject to pressure, the insulatingmaterial is interposed between the conductors, as in FIG. 5( b),ensuring physical separation. However, when subjected to pressure normalto the plane of the fabric, the encircling insulating material cantwist, compress, move aside or otherwise deflect to allow electricalcontact between the core conductor yarns, as FIG. 5( c) shows. Uponremoval of the applied pressure, the insulating material springs backinto position and/or shape between the conductors to break (open) theelectrical contact.

The geometry of the composite yarn and the compressibility, stiffnessand surface textures of its constituent yarns contribute to determiningthe pressure threshold of a crossover point and can readily bedetermined by experiment. Composite yarns of this type may be used toconstruct plain weave crossover points, without the float structuresdescribed above.

Separation Technique—Compressible, Insulating Cored Yarn Encircled withConductor

Another separation technique involves another type of compositeconstruction for the conductive yarns. In this composite yarn, which isa reverse case of the yarn detailed above, an insulating mono-filamentor multi-filament core yarn is twisted, spun, braided, plaited,co-extruded, coated, sleeved or otherwise partially encircled byconductive yarns or material.

Additionally or alternatively, a conductive core may be co-extruded withan insulating coating and then subjected to post production processingto selectively expose areas of the conductive core. The conductive yarnsare partially embedded into the insulating core yarn, such that thecompressible, yielding surface of the core yarn stands proud of theconductive yarns, as shown in FIG. 6( a). Alternatively, but to the sameend, thin conductive yarns may be twisted or spun with larger insulatingyarns such that the insulating yarns stand proud of the conductiveyarns.

When a crossover point between two conductive yarns, at least one ofwhich is of this nature, is not subject to pressure, the insulatingmaterial that stands proud of the conductive yarns ensures physicalseparation of the conductors, as FIG. 6( b). However, when subject topressure normal to the plane of the fabric, the insulating material cancompress to allow electrical contact between the embedded conductoryarns, as shown in FIG. 6( c). Upon removal of the applied pressure, theinsulating material springs back into position to hold the conductorsapart and break the electrical contact.

The geometry of the composite yarn and the compressibility, stiffnessand surface textures of its constituent yarns contribute to determiningthe pressure threshold of a crossover point and can be readilydetermined by experiment. Composite yarns of this type may be used toconstruct plain weave crossover points, without the float structuresdescribed above.

Separation Technique—Conductive Cored Yarn Encircled with DisplaceableInsulator

Referring to FIGS. 7( a) to 7(c), there are shown various embodiments ofyarn with both insulator and conductor. In FIG. 7( a) there is a coreyarn substantially circular in cross-section which can be insulating orconductive as desired. Spun, braided or twisted around the core thereare larger diameter insulating yarns and smaller diameter conductiveyarns. As can be seen in the Figures, when no pressure is applied to theyarn, the conductive fibres remain spaced from the other conductor(s).However, upon application of a compressing force above the threshold,the insulating yarns are compressed and/or moved to allow contact of theconductive yarns on the conductive base (which may be another compositeyarn of this type).

In FIG. 7( b) there is simply a conductive core having coated thereon orextruded therewith one or more insulating ribs, preferably in a helicalarrangement. As can be seen, when no pressure is applied, the conductivecore remains spaced from any conductive base upon which the composite isplaced (the base may be the another composite structure such as this).However, upon application of a compressive force, there is compressionof the insulating rib(s) to allow electrical contact.

In FIG. 7( c) a deformable conductive core has formed therewith aninsulating sleeve from which sections are then removed to leave grooveswith conductive troughs. Compression of the structure will causedeformation of the grooves such that a conductive substrate, which mayfor example be a plate or fibre-like conductor, will make electricalcontact with the conductive core. It is not necessary for any part ofthe conductive core to be removed to create the groove, merely to enoughinsulator to be removed to allow access to the core.

Separation Technique—Self-Separating Sensory Composite Yarn

In FIG. 8 there is shown an embodiment of composite yarn having a corearound which there is braided a conductive/insulating yarn with floatingconductors, which enables the detection of pressure applied at a pointalong the length of the structure.

Parameters Controlling Actuation Pressure

A number of controllable manufacturing parameters determine theactuation pressure of a crossover point between two conductors in awoven piece of fabric.

a) Relative Diameters of Conductive and Insulating Yarns

As discussed above, if the conductive yarns in the weave are of asmaller diameter or cross-section than the insulating yarns, theconductive yarns at a crossover point are separated by a greaterdistance. The conductive yarns must be deflected further in order tomake contact, thus requiring a greater actuation pressure.

b) Propensity of Conductive Yarn to Make Electrical Contact

A number of variables contribute to the propensity of a conductive yarnto make mechanical electrical contact. Conductive yarns with very smoothand/or hard surfaces tend to smaller areas of contact than fibrousand/or compressible yarns when contacted together under similarpressures. Mono-filament conductors of circular cross-section similarlyoffer less contact area than prism shaped or multi-filament yarns.Specifics of the composite yarns are described above.

c) Fabric Stiffness

The actuation pressure required to deflect the conductors at a crossoverand make electrical contact is directly governed by the stiffness of theconductive and surrounding insulating yarns, and the general stiffnessof the fabric, which in turn is governed by the weave structures used,the yarn spacing and the level of weft compacting, or beat, used.Stiffer fabric requires a greater force for a given deflection and willtherefore result in crossovers of greater actuation pressure.

d) Number of Adjacent Conductive Yarns

If multiple adjacent conductive yarns are used instead of a single warpor weft conductive yarn, as in FIG. 9( a), the actuation pressure isreduced. Wider conductors with a greater number of adjacent yarns, asshown in FIG. 9( b), both offer a larger contact area at a crossoverpoint and require less angular deflection of the yarns, and thus lesspressure, to make contact.

e) Number of Yarns Floated

If a conductive weft yarn is floated over a minimum number of warp yarnsto ensure separation at a crossover point, as shown in FIG. 9( a), theactuation pressure is correspondingly lesser than if the conductive weftis floated over a larger number of adjacent warp yarns, as shown in FIG.9( c).

Implications to Note on Actuation Pressures

Controlling the aforementioned manufacturing parameters allows crossoverpoints with predetermined actuation pressures to be woven into a pieceof fabric. The threshold pressures for both electrical contact to bemade and maximal contact to be achieved can be determined independently.Crossover points with different pressure thresholds may be incorporatedinto a single piece of fabric. This enables the construction of, forinstance, a group of neighbouring crossover points that make contactconsecutively with increasing pressure and together constitute aquantised pressure sensor.

Another implication of controlling the parameters at a crossover pointis that the two conductive yarns may be woven to be in permanentelectrical contact, regardless of applied pressure. Principally, thismay be achieved through the use of a plain weave structure at thecrossover point, where the conductive weft is not floated over anyadditional warps, but instead shares a large, permanent contact areawith the conductive warp yarn. This allows, for instance, the wovenconstruction of bus-bars, discussed herein.

Conversely, if the actuation pressure threshold of a crossover point ismade very large, the two conductive yarns may be woven such that theynever make electrical contact under typical operating conditions. Thisallows two conductors to pass over one another and remain electricallyindependent. This facility to design crossover points that make or failto make contact within a grid of conductors allows the routing ofcurrent throughout the piece of fabric akin to the tracks of a printedcircuit board.

Addressing the Matrix of Crossovers

Each crossover point between two conductors may be treated as anindependent switch, with the array of crossovers constituting arow-column addressed matrix, similar to the majority of existingkeyboards. In order to achieve this, each conductive yarn must beindividually connected to a suitable circuit for scanning the matrix.Making this number of connections to the piece of fabric can proveinconvenient.

Alternatively, a scheme which requires far fewer connections to thepiece of fabric is to address the matrix of crossovers throughelectrical bus-bars, as shown in FIG. 10. These bus-bars each serve tointerconnect the conductors of one set. The number of connections to thepiece of fabric does not scale with the number of crossovers.

The bus-bars may be sewn, embroidered, printed, adhered, mechanicallyclamped or crimped to the piece of fabric in order to make electricalcontact with the matrix of conductors. Most attractively, they can alsobe of woven construction, integral to the piece of fabric in a similarmanner to the matrix. A typical arrangement is also shown in FIG. 10.

Some reproducible electrical characteristic, for example resistivity,can be measured to ascertain the length of a conductor and/or bus-bar.The position of a “closed switch” at a crossover in the matrix can bededuced from these measurements.

For example, first assume that the conductive yarns of the matrixexhibit a linear resistivity, and that connections are made to threeperfectly conductive bus-bars as shown in FIG. 10. If the switch atcrossover point D is closed, the resistance RAB measured from bus-bar Ato bus-bar B is given by:RAB=K(X+Y)

where K is a constant determined by the absolute lengths,cross-sectional areas and resistivities of the conductive yarns, anddistances X and Y are the orthogonal vector components of point D, where0<=(X,Y)<=1.

Similarly, the resistance measured from bus-bar B to bus-bar C is givenby:RBC=K(Y+1−X).

Substituting gives:X=[((RAB)/K)−((RBC)/K)+1]/2

and:Y=[((RAB)/K)+((RBC)/K)−1]/2.A Typical Example

This section details an example of weaving instructions for constructinga typical piece of fabric. A piece of fabric of arbitrary size may bereproduced from these specifications, although the repeat for a 250 mmwidth has been included. The crossover points are evenly spaced in agrid some 8.5 mm apart. Using the specified yarns and weave structures,the pressure threshold of the crossover points is roughly 80kiloPascals, equivalent to 4 Newton force on a typical fingertip area of50 square millimetres. The specifications also incorporate two bus-barsin the warp yarns, at either side of the piece of fabric.

The warp has been designed with two selvedge edges consisting of atwisted multi-filament yarn, BASF F901 G004, 8 warp threads at eitheredge of the warp on shafts 1-4, shown diagrammatically in FIG. 10( a).

The warp continues to use a 100% cotton 2/18's yarn set at 24 ends perinch. This is interspersed with conductive mono-filament type BASF F901A013 every 8 warp threads on shafts 8, 16 and 24.

The lifting sequence/peg plan determines the order in which the shaftsare moved to lift or leave the warp threads.

A weft thread of the same cotton is passed through the shed of liftedwarp threads, as in the peg plan of FIG. 10( b) and substituted with theconductive mono-filament F901 A013 on every 6th pick. This determinesthe weft thread floats over the conductive warp threads.

Individually Addressable Multiplexed Switches within a Woven FabricConstruction

FIG. 12 shows an embodiment of individually addressable multiplexedswitches which can be formed form any of the embodiments describedabove. As can be seen, a grid of conductor crossover points areproduced, by any of the above-described methods, and two bus barsprovided with the permanent electrical connections as shown in theFigure. The switches provide, when closed, the closed circuits as shownin the example matrix configurations. More specifically, when each inputline D* is connected to a positive potential in turn, the threeresulting 3-bit patterns produced at the outputs Q1, Q2, Q3 uniquelyidentify a closed switch within the matrix of crossovers. Connecting thematrix to the inputs D1, D2 and D3 and outputs Q1, Q2 and Q3 accordingto a binary code allows more graceful response to multiple closedswitches therein.

1. A pressure sensor fabric provided with a single layer including warp and weft filaments within said single layer, wherein: a. the warp filaments include at least one first elongated electrical conductor and the weft filaments include at least one second elongated electrical conductor, b. the warp and weft filaments extend across and within a common plane within the layer, wherein the warp and weft fibers both include portions resting on opposite sides of the plane, said first conductor or conductors being crossed by said second conductor or conductors, said conductors being normally biased apart at a crossover point of said conductors with an air gap between them resulting from insulating fibers or filaments which bias the first and second conductors apart at the crossover point wherein application of pressure in a direction substantially normal to a plane of the fabric is required to cause the conductors to make direct conductive contact wherein the air gap between them is closed with the conductors touching, with such contact changing the conductive properties of the fabric and thereby allowing sensing of the pressure.
 2. A fabric according to claim 1, including a plurality of spaced first conductors and/or a plurality of spaced second conductors, forming a plurality of said crossover points.
 3. A fabric according to claim 1, wherein said biasing apart is effected locating an electrical conductor of relatively smaller cross-section between insulating filaments or fibers of relatively larger cross-section.
 4. A fabric according to claim 1, wherein the weave includes warp and/or weft floats over more than one yarn to effect the biasing apart of first and second electrical conductors at the crossover point.
 5. A fabric according to claim 1, wherein said biasing apart is effected by employing, as at least one of the electrical conductors, an electrical conductor including insulating filament or fiber wound around it to leave the surface of the conductor exposed at the crossover point.
 6. A fabric according to claim 1, wherein said biasing apart is effected by twisting at least one of the electrical conductors together with insulating filament or fiber.
 7. A fabric according to claim 1, wherein said biasing apart is effected by employing, as at least one of the electrical conductors, a fiber including an insulating yarn and a conductive yarn, the insulating yarn including portions extending beyond the conductive yarn.
 8. A fabric according to claim 7, wherein there are provided two or more conductive yarns helically wound around the insulating yarn.
 9. A fabric according to claim 1, wherein the electrical conductors have an electrical property which is proportional to the length of the conductor, whereby the length of a conductor or plurality of connecting conductors can be determined from measurement of that property.
 10. A fabric according to claim 1, including at least one set of spaced electrical conductors, at least some of said set being electrically connected together to form at least one bus bar.
 11. A fabric according to claim 10, wherein said set of spaced electrical conductors comprises electrically conductive filaments or fibers in the warp or weft of a woven construction and electrical connection between conductors of that set is provided by one or more electrically conducting filaments or fibers in the well or warp, respectively.
 12. A fabric according to claim 10, wherein said set of spaced electrical conductors comprises electrically conductive filaments or fibers in the warp or weft of a woven construction and said electrical connection is made after the weaving process.
 13. A pressure sensor fabric comprising a sheet which includes therein: a. an elongated first conductor, and b. an elongated second conductor crossing the first conductor, c. an insulator maintaining the first and second conductors in spaced relation with an air gap therebetween at the location within the fabric at which the first and second conductors cross, the insulator running alongside at least one of the first and second conductors over a major portion of its length, wherein: (1) the first conductor, second conductor, and insulator are all present within a single layer of the fabric, wherein the first conductor, second conductor, and insulator all extend across and within a common plane, with the first conductor, second conductor, and insulator all having portions resting on opposite sides of the plane; (2) applying pressure to a portion of the plane of the fabric is required to displace the insulator and move the first and second conductors into conductive contact with the first and second conductors touching each other, thereby changing the electrical properties of the fabric and providing a sensor signal indicative of the pressure.
 14. The fabric of claim 13 wherein the diameter of the insulator is greater than the diameter of at least one of the conductors.
 15. A sheet of pressure sensor fabric comprising: a. several elongated first conductors oriented in at least substantially parallel relationship, and b. several elongated second conductors oriented in at least substantially parallel relationship, the second conductors crossing the first conductors, c. several elongated insulators, each i) extending alongside at least one of the first and second conductors over a major portion of its length and ii) maintaining the first and second conductors in spaced relation with an air gap therebetween at the locations at which the first and second conductors cross wherein: (1) the first conductors, second conductors, and insulators are all present within a single layer of the fabric, wherein the first conductors, second conductors, and insulators all extend about a common plane, with the first conductors, second conductors, and insulators all having portions extending between opposite sides of the plane, and (2) applying pressure to a portion of the plane of the fabric is required to move the first and second conductors into direct conductive contact with the first conductor touching the second conductor, thereby altering the conduction of the fabric to allow sensing of the pressure.
 16. The sheet of claim 15 wherein each insulator extends alongside and in contact with at least one of the first and second conductors over a major portion of its length.
 17. A fabric according to claim 1 wherein the first conductor, second conductor, and insulating fibers are interwoven within the common plane.
 18. A fabric according to claim 1 wherein the first conductor weaves above and below a plane wherein the second conductor is situated.
 19. A fabric according to claim 1 wherein sections of both the first conductor and the second conductor are exposed on both of the opposite sides of the layer.
 20. The fabric of claim 13 wherein the first conductor, second conductor, and insulator are interwoven within the common plane.
 21. The fabric of claim 13 wherein the first conductor weaves above and below a plane wherein the second conductor is situated.
 22. A fabric according to claim 13 wherein sections of both the first conductor and the second conductor face outwardly from both of the opposite sides of the layer.
 23. The sheet of claim 15 wherein the first conductors, second conductors, and insulators are interwoven within the common plane.
 24. The sheet of claim 15 wherein the first conductors weave above and below a plane wherein the second conductors are situated.
 25. The sheet of claim 15 wherein sections of both the first conductors and the second conductors are situated at outermost portions of both of the opposite sides of the layer. 